Extrapancreatic origin of the pancreatic secretory trypsin inhibitor as an acute-phase reactant

The aim of the present investigation was to study the origin of the elevated levels of the pancreatic secretory trypsin inhibitor (PSTI) seen in the bloodstream during an acute-phase reaction. PSTI and cationic trypsinogen levels in pancreatic juice and plasma from five patients were measured over 8 days following subtotal pancreatoduodenectomy (Whipple's procedure). Cells from a human hepatocellular carcinoma cell line (Hep G2) and from a human pancreatic cancer cell line (CAPAN-1) were cocultured with endotoxin-stimulated mononuclear white blood cells using a double-chamber technique. Hep G2, CAPAN-1, and mononuclear white blood cells were also cultured as single populations. The median plasma level of PSTI increased from 16.6 micrograms/L at the time of surgery to 155 micrograms/L at the fourth postoperative day. No increase in PSTI levels in pancreatic juice or trypsinogen levels in pancreatic juice and plasma was observed. Culture medium from stimulated hepatocellular carcinoma cells contained significantly elevated levels of PSTI compared with the levels of PSTI from unstimulated cells. Culture medium from pancreatic cancer cells alone contained high levels of PSTI but no difference was observed compared with PSTI levels in medium from stimulated pancreatic cancer cells. The mononuclear white blood cells did not produce PSTI. The results support the view of an extrapancreatic origin of plasma PSTI during the acute-phase reaction and indicate that the liver is the probable source.